Signs of autism begin to show in children as young as six months after birth. Signs of the presence of this disorder appear during infancy and it is usually diagnosed by the age of three years. This time is allowed as an autistic child aged two years old can appear to be normal, but it is after three years that one can jump to a conclusion. After about two and two and a half years, the symptoms will appear to regress rapidly. They can appear at various levels i.e. they can begin gradually and pick up in pace thereafter or they can just appear in an exaggerated manner.

Newborns with this disorder will be seen to display abnormal reactions to sensory stimuli. This means that their senses may appear to be overactive as compared to a normal child. The exact opposite behavior of being excessively dormant can also appear. Generally, there are some regular traits that one can lookout for. For instance, a child may appear to feel pain whenever they are touched. In this case, they will tend to seclude themselves and often hold their hands close to their bodies .

Another trait can be witnessed in their reaction to a foul smell, they may react unusually. Their reaction to it may be somewhat exaggerated as compared to how a normal person would. Another unusual behavior would be in their response to the day to day noises that surround them. Also, loud noises like those caused by a motorcycle going by, vacuum cleaner or even the presence of bright lights in a room may cause inconsolable crying in an autistic child.

Withdrawal behaviors in a child where they tend to be happier alone can also be a justified reason to suspect autistic characteristics in a child. They may display a lack of interest in toys, lack of response to others, a marked reduction or increase in activity level or an ultimate resistance to cuddling.

Young children with autism are known to have impaired language development. Autistic children also have difficulty in communication their needs. They tend to use sign language to communicate or general body language like crying to express dislike or laughing to express their liking for something. They also develop an unclear and underdeveloped method of expressing their needs. They may at times make use of their incomplete speech which mostly does not make much sense. Some may experience echolalia which is a trait depicted by the repetition of many words in a sentence. All these are characteristics of autistic children and there is need to know them traits so that it can be easy to identify an autistic child.